Reply to "Ford 400 FMX Block - D1AE-6015-A2C - All original"

The rear of the FMX block has a dual bell housing pattern, and is drilled & tapped for small block Ford bell housings, whereas the standard 400 block has only one pattern which is designed for big block Ford bell housings. That's why its called the FMX block, it was cast to enable the use of FMX automatic transmissions with the small block bell housing (see picture at bottom).

There is another 351M/400 block designed for trucks, D7TE casting code, it is a "heavy duty" block, reinforced bulkheads and perhaps extra iron in other key places to add strength. It came about because the 351M and 400 replaced the 360 & 390 FE truck engines beginning 1977. A year later the passenger car line got a heavy duty block as well, casting code D8AE.

All 351M/400 engines have the same 3" main bearing journals, same size as a 351W (351 Cleveland is 2.75").